An EMD based method for detrending RR interval series without resampling

Slow trends in the RR interval（RRI） series should be removed in the preprocessing step to get a reliable result of heart rate variability（HRV） analysis. Re-sampling is required to convert the unevenly sampled RRI series into evenly sampled time series when using the widely accepted smoothness priors approach（SPA）. Noise is introduced in this process and the information quality is thus compromised. Empirical mode decomposition（EMD） and its variants, were introduced to directly process the unevenly sampled RRI series. Besides, a RR interval model was proposed to fascinate the introduction of standard metrics for the evaluation of the detrending performance. Based on standard metrics including signal-to-noise-ratio in d B（ISNR）, mean square error（EMS）, and percent root square difference（DPRS）, the effectiveness of detrending methods in RR interval analysis were determined. Results demonstrate that complementary ensemble EMD（CEEMD, a variant of EMD） based method has a higher ISNR, a lower EMS and a lower DPRS as well as a better RRI series detrending performance compared with the SPA method, which would in turn lead to a more accurate HRV analysis.